Since a carbon nanomaterial having a sharp-pointed tip shape and the high aspect ratio including a carbon nanotube (hereinafter, referred to as CNT) is suitable for field emission, many developments have been conducted as a field emission display (FED) or an electron release source such as a backlight for a liquid crystal using field emission. The electron emission source using CNT can be manufactured by printing a paste obtained by mixing CNT with a binder and an organic component such as a solvent and the like, on a cathode electrode, followed by firing.
In order that CNT effectively emits an electron, good electric contact between CNT and a cathode electrode is important. However, due to the presence of an insulating component such as amorphous carbon which is the firing residue of impurities of CNT and organic components, and a glass powder which is added for imparting adhering property between a cathode electrode and CNT, good electric contact is inhibited in some times.
Then, the technique of imparting electrical conductivity by mixing a silver particle so as to retain electric contact has been published (see Patent Document 1). In addition, the technique regarding a paste for an electron source containing at least a metal fine particle or a metal oxide fine particle having the particle diameter which is approximately 10-fold or less of the wire diameter of a needle-like substance such as CNT, in the needle-like substance such as CNT having the wire diameter of approximately 100 nm or less, for the purpose of uniformly dispersing CNT without bundling has been disclosed (Patent Document 2).
However, in the technique disclosed in Patent Document 1, electric contact with a cathode electrode of CNT could not be preferably retained depending on the particle diameter of a silver particle, in some cases. In addition, also in the technique disclosed in Patent Document 2, since the particle diameter of a metal fine particle, or metal oxide having electrical conductivity is small, this did not lead to better electric contact.    [Patent Document 1] Japanese Patent Application Laid-Open (JP-A) No. 2004-504690 (paragraph 21)    [Patent Document 2] JP-A No. 2005-222847 (claims 1, 2)